The present invention relates to a method and apparatus for manipulating web- or strip-shaped materials, especially for supplying such materials to processing machines. Typical examples of processing machines which utilize web- or strip-shaped wrapping materials are cigarette packing machines wherein arrays of e.g., four, five, ten, twenty or twenty-one cigarettes are confined in wrappers consisting of paper, tinfoil, synthetic plastic material or a combination of two or more envelopes.
It is already known to convert the leader of a strip of wrapping material into a loop prior to delivery into the processing machine. Reference may be had to German Offenlegungsschrift No. 22 05 366 or to German Offenlegungsschrift No. 31 14 470. These publications disclose apparatus wherein the loop at the leading end of a strip of wrapping material is introduced into a magazine at a continuously varying or variable speed, and successive increments of the loop are intermittently withdrawn from the magazine for admission into the processing machine. In order to hold the loop in the magazine, the apparatus which are disclosed in the German publications further comprise suction generating means for attracting the bight of the loop.
A drawback of the aforedescribed conventional apparatus is that their operation is unsatisfactory when the frequency at which increments of the wrapping material must be withdrawn from the magazine exceeds a certain value. The strip is then agitated to such an extent that it can affect the accuracy and predictability of withdrawal of increments of preselected length and cause improper operation of the processing machine. This can result in the making of a large number of defective packs and in a pronounced reduction of the output of the processing machine, e.g., a high-speed cigarette packer which turns out several hundred packs per minute.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved apparatus for supplying strips or webs of wrapping or like material to processing machines at any desired practical frequency without affecting the accuracy and predictability of admission of the material into the processing machine.
Another object of the invention is to provide the apparatus with novel and improved means for eliminating or at least strongly damping stray movements of a strip of wrapping or like material on its way to a processing machine which receives the material at a certain frequency rather than continuously.
A further object of the invention is to provide the apparatus with novel and improved means for damping or preventing stray movements of the conveyed material in the magazine which stores a length of such material in the form of a loop.
An additional object of the invention is to provide the apparatus with novel and improved means for synchronizing the movements of various mobile units so as to ensure a predictable rate of material feed into the magazine.
Still another object of the invention is to provide a novel and improved loop forming magazine for use in the above outlined apparatus.
An additional object of the invention is to provide an apparatus which allows for high-frequency or low-frequency withdrawal of predetermined lengths of strip-shaped material from the magazine wherein the material is confined in the form of a loop.
Another object of the invention is to provide a novel and improved method of supplying strip- or web-shaped material, especially webs of tinfoil, paper or the like, to a high-speed processing machine, such as a cigarette packing machine.
A further object of the invention is to provide a novel and improved method of preventing or reducing the extent of stray movements of looped strip- or web-shaped material in the magazine of the above outlined apparatus.
Another object of the invention is to provide a method which ensures that the integrity of the conveyed material is not affected by the selected frequency at which predetermined lengths of the material must be withdrawn from a magazine wherein the leader of the material is stored in the form of a loop.
The improved apparatus is utilized to supply strip- or web-shaped wrapping material to a processing machine, particularly to a cigarette making machine, and comprises a source of wrapping material (e.g., a bobbin of convoluted tinfoil, paper or the like), a magazine, means for feeding wrapping material from the source into the magazine and for converting the wrapping material in the magazine into a loop (the configuration of the magazine may be such that it promotes the formation of a loop therein), and means for intermittently withdrawing wrapping material from the magazine with attendant changes in the dimensions of the loop and a tendency of the loop to become agitated (such tendency is more pronounced when the frequency at which the wrapping material is being drawn from the magazine increases, e.g., to satisfy the requirements of a packing machine which turns out four hundred or more cigarette packs per minute). The magazine has a portion (preferably an upstanding sidewall) which is adjacent to a part of the loop therein, and the improved apparatus further comprises means for opposing agitation of the loop. Such opposing means is adjacent to the aforementioned portion of the magazine and acts upon the aforementioned part of the loop. The loop in the magazine has a bight which is or can constitute the lowermost portion of the loop and two legs which flank the bight. One of these legs preferably constitutes the aforementioned part of the loop.
The opposing means preferably constitutes or comprises an endless foraminous conveyor one side of which is adjacent to the aforementioned portion (sidewall) of the magazine, and means (e.g., a suction chamber) for pneumatically urging the aforementioned part or leg of the loop against the aforementioned side of the conveyor. The suction chamber is connected to the intake of a fan or another suitable suction generating device.
The apparatus preferably further comprises means for driving the conveyor at a speed which preferably slightly exceeds the speed at which the feeding means delivers wrapping material into the magazine so that the conveyor maintains the aforementioned part or leg of the loop under tension (to this end, the conveyor is driven in a direction to advance the wrapping material in the direction in which the material is being delivered by the feeding means). The conveyor can comprise one or more endless foraminous belts and the apparatus preferably further comprises means (e.g., a battery of sensors in the form of proximity detectors) for monitoring the dimensions of the loop in the magazine, preferably in the region of the aforementioned portion or sidewall of the magazine. The sensors are preferably disposed one after the other, as considered in the direction of feed of wrapping material into the magazine. The conveyor can comprise a single and preferably wide endless foraminous belt having a stretch which is adjacent to the sidewall of the magazine and means for pneumatically attracting the aforementioned part of the loop to such stretch; the monitoring means is then adjacent to one side of the stretch. Alternatively, the conveyor can comprise two relatively narrow endless foraminous belts whose stretches flank the monitoring means.
The source of wrapping material can be disposed at a level above the magazine and the latter is then formed with an open top for admission of wrapping material into its interior. Such magazine is formed with a bottom wall which causes the admitted wrapping material to develop a bight adjacent to the bottom wall and two legs adjacent to two sidewalls forming part of the magazine, extending upwardly from and disposed at the opposite sides of the bottom wall. Each leg of the loop in the magazine is adjacent to the inner side of a different sidewall. That leg which is adjacent to the aforementioned portion or sidewall of the magazine travels downwardly toward the bottom wall, and the withdrawing means can comprise a tongs which is constructed, mounted and operated to intermittently draw predetermined lengths of the other leg of the loop through the open top of the magazine.
The feeding means can comprise a pair of rotary advancing elements and the apparatus can further comprise means for driving the conveyor or conveyors as well as for driving at least one of the rotary advancing elements in synchronism with the conveyor. The driving means is preferably adjustable by the aforementioned monitoring means as a function of changes in the dimensions of the loop in the magazine.
Another feature of the invention resides in the provision of a method of supplying strip-shaped wrapping material to a processing machine, such as a cigarette packing machine. The method comprises the steps of establishing and maintaining a source of supply of wrapping material (e.g., a reel of convoluted wrapping material), feeding the wrapping material from the source at a variable speed along a predetermined path and converting the leader of the advancing wrapping material into a loop having a bight and two legs or flanges flanking the bight, intermittently drawing wrapping material from one leg of the loop with attendant changes in the dimensions of the loop and a tendency of the loop to become agitated, and opposing such agitation of the loop including maintaining the other leg of the loop in the respective portion of its path. The maintaining step can include pneumatically urging the other leg of the loop into the respective portion of the path, tensioning the other leg of the loop in such portion of the path and/or conveying the other leg of the loop along the respective portion of the path at a speed which deviates from the variable speed. The method can further comprise the step of monitoring the dimensions of the loop and varying the speed at which the wrapping material is being fed from the source as a function of changes in the dimensions of the loop.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.